Logic Riddles

Question: If a white house is white and a yellow house is yellow, what color is a green house?

Question: A man was found dead in his study. He was slumped over his desk and a gun was in his hand. There was a cassette recorder on his desk. When the police entered the room and pressed the play button on the tape recorder they heard: "I can't go on. I have nothing to live for." Then there was the sound of a gunshot. How did the detective immediately know that the man had been murdered and it wasn't a suicide?

Question: 7 months have 31 days. How many months have 28 days?

Question: You are my brother, but I am not your brother. Who am I?

Question: If you have an 11 minute and 13 minute hourglass, how can you accurately time 15 minutes?